1. Field of the Invention
The invention relates to an arrangement and method for removal of contaminant deposits, and in particular to a plasma generator for removing contaminant deposits.
2. Description of the Related Art
The accuracy and reliability of charged particle lithography systems is negatively influenced by contamination. An important contribution to contamination in such lithography system is caused by the build-up of deposits of contaminants. Charged particle lithography systems generate charged particles such as electrons, and generate beams of charged particles which are focused, modulated and projected onto a wafer in the lithography process. The charged particle beams interact with hydrocarbons present in the lithography system, and the resulting Electron Beam Induced Deposition (EBID) forms a carbon-containing layer on surfaces in the system. This layer of carbon-containing material affects the stability of the charged particle beamlets. The charged particle beams and beamlets are typically formed using aperture plates, and they may also be focused and modulated by arrays of lenses and electrodes formed in aperture plates. A build-up of carbon-containing layers in and around apertures through which the charged particle beams or beamlets pass also reduces the size of the apertures and reduces transmission of beams or beamlets through these apertures. Removal of EBID, in particular in areas with relatively high hydrocarbon partial pressures and relatively high beam current densities, is therefore highly desirable.
Such deposits can be lessened or removed by atom cleaning. This may be achieved using a plasma generator to produce a stream of atomic radicals that chemically react with the deposits, forming volatile molecular compounds.